looks like industry standard now is 14.4 volts. I cant believe how overpriced most of these car audio stores are. Unreal, I see how the car audio business is failing when its over double the price as online.

If you are trying to do this sub in a marine environment , I would stick to a marine sub. A marine sub is made for the extreme environment of a boat and for the inherently weird sized enclosures that they have. All of the subs except for the wet sounds one are car audio subs. If you are going to take a spot on your boat, lets say in a lift off area of a seat . And build a enclosure that is the correct volume and tuned with a port . It has to be completely sealed except for the port in the box, Then you will have to integrate this enclosure in the area you have with fiberglass and seal it in perfectly . If you are willing to do this a car sub will be fine . If not then go with a real marine sub. This is how you mount a marine sub. You find a compartment and cut a hole then screw a marine sub in wire it up and rock on! The reason a marine sub is better has almost nothing to do with the water . It works better because they know most people are just going to put them in a seat compartment and not calculate the shit out of the actual volume of a odd area and try to make it airtight. Alpine makes a 10" SWR M100 sub that a retard could install and have amazing results with. It costs around 230.00 so it is not expensive . Trust me , if you are doing the work yourself you are going to like just cut a hole mount it and rock . It's theil small parameters are made like the old free air subs ,so it will take a huge cabinet or smaller one and it doesn't have to be airtight . I carry Digital Designs subs and have put them on a boat and I can tell you how much work it takes for a pro to do it right . I call it my bend over, if you have to ask you can't afford it price list By the way a Digital Designs 9500 12 starts at 900 without any options , the Z series are 2200 each in a 12. I would go the Alpine SWR M100 NOT the Type R Or the RE subs. If you want it really loud do multiples of the 10 ,yopu will be very happy I hope this helps you out.